Male cones in Pinus are small structures that are present together in clusters. They consist of several microsporophylls that bear microsporangia which produce the pollen grains. Here, let’s discuss more about the Pinus male cone.
Table of Contents
Pinus
Pinus is a genus of large, evergreen, coniferous, perennial plants that usually have a pyramidal or conical appearance. They comprise a long-lived plant species which mostly include trees and very rarely shrubs. Pinus consists of resinous trees that are mostly significant for their wood pulp and timber. Examples – P. densata, P. roxburghii, P. radiata, etc.
It is a monoecious genus where the female and male flowers are present in the same form of strobili or cones on separate branches of the same plant. Its sporophytic plant body can be distinguished into stem, roots and leaves (pine needle).
Pinus Male Cone
Gymnosperms have seed-bearing structures called cones. Female cones of pine are typically larger than male cones. The cones are surrounded by many scales. A male pine cone is usually less woody than a female pine cone. Also the male cones contain pollen, whereas female cones contain seeds.
Pine cones (male) can be found at the bottom of a new shoot in clusters. Once all of their pollen has been released, they wither and eventually fall off. Pinus is a monoecious plant. Seed cones and pollen are often seen on the same plant, but not on the same shoot.
The pollen cone or male strobilus is basically a branch that has been modified. Microsporophylls are the leaves. These modified leaves contain microsporangia, which produce pollen grains. Each sporangium contains numerous small dots that are pollen grains. Let’s have a look at the structural description of a male pine cone.
Related Topic:Difference between Cycas and Pinus
Structural Development of Male Cone in Pine
Each Pinus male cone is oval or ovoid in shape and not very large. The pollen cones in most Pinus species are generally green, which then turn yellow and finally golden brown in colour upon dehiscence.
- The male cone has many microsporophylls attached spirally to a central axis. Pinus microsporophylls are short-stalked, scaly, membranous, and thin. A microsporophyll is typically compared with the stamen of an angiosperm.
- Each microsporophyll has sporangial sacs on its abaxial surface. Only 2 microsporangia remain side by side on the bottom or abaxial surface of each microsporophyll. Microsporangia are also seen in the adaxial surface of each microsporophyll.
- Some microsporophylls on the lower side of the male cone are sterile.
- The microsporangial cells divide in various planes, creating a mass of sporogenous cells which will later undergo meiosis.
- The product of each meiosis will result in a tetrad of 4 microspores. Each single-celled microspore or pollen grain will eventually be protected by a spore wall.
Pollen grain – It is a male gametophyte enclosed in a spore wall secreted by sporophyte-derived tapetal cells. This spore wall or exine protects the pollen grain from early development in the sporangial sac and also protects from harsh conditions. Each microspore (pollen grain) also has a thin inner covering called intine. It is usually the exine that protrudes out in the form of wings and helps in the dispersal of pollen grains.
The release of pollen usually begins at the proximal end of the male strobili and then progresses acropetally. Finally, when the pollens are released completely, the male strobilus becomes dry and brown in colour.
Explore more such key concepts with regards to NEET, only at BYJU’S.
Also Check:
Recommended Video:
Comments